Filter



FIG. 1 is a perspective view of a filter as seen from one side showing my new design;

FIG. 2 is a perspective view thereof as seen from the opposite side;

FIG. 3 is a perspective view of a second embodiment of the filter as seen from one side;

FIG. 4 is a perspective view thereof as seen from the opposite side. 

The ornamental design for a filter, substantially as shown and described. 